|Estell, Richard - Rick|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/16/1997
Publication Date: N/A
Interpretive Summary: In many arid regions of the world, grasslands have turned into shrublands. Shrub species in the Chihuahuan Desert are not usually eaten by livestock, and these shrubs often contain noxious chemicals. Understanding the role of plant chemicals in controlling shrub consumption by animals may help us to find ways to alter the amount of a particular plant species eaten by livestock. We are studying how one group of chemicals (terpenes) on the leaf surface affects the amount of tarbush eaten by cattle and sheep. In an earlier study, we found that when areas infested with tarbush were densely stocked for a few days, the amount of leaves eaten varied greatly among plants. Certain terpenes appeared to be related to diet selection in earlier studies. We applied some of these chemicals individually to palatable feeds to determine if they directly affected preference of sheep. In six experiments we measured the effect of a compound (camphor, limonene, ,cis-jasmone, beta-caryophyllene, borneol, or alpha-pinene) on consumption of alfalfa pellets. Two compounds (alpha-pinene and camphor) were negatively related to intake. Our results suggest certain compounds may be partly responsible for variable use of tarbush by livestock, while others were not important when examined individually.
Technical Abstract: Experiments were conducted to examine effects of six volatile compounds on alfalfa pellet consumption by lambs. In each experiment, 45 lambs were individually fed a selected compound (camphor, limonene, cis-jasmone, beta- caryophyllene, borneol, or alpha-pinene) at one of five concentrations for 5 d. Treatment concentrations were multiples (0, .5, 1, 2, and 10) of the concentration of a specific compound (X) that was related to differential herbivory of tarbush by livestock in previous studies. Treatments were applied to alfalfa pellets (.64 kg.lamb-1.d-1, DM basis), and consumption was measured during a 20 min interval each morning. Lambs were adapted to handling procedures and the pelleted diet (without treatments) for 10 d. Lambs were maintained and fed (approximately 4.5 to 5% of BW) as one group except during 20 min tests. A treatment effect was observed for borneol (P< .04), with pellet consumption for the 2X treatment greater than for the 0X, 1X, or 10X treatments (P < .10). A treatment effect was also detected for alpha-pinene (P < .05), with intake for the 10X treatment less than for the 0X, .5X, or 1X treatments (P < .10). Camphor tended to affect pellet consumption (P < .08), with intake for the 10X treatment less than for the 0X or 1X treatments (P < .10). The other three compounds had no discernable effect on consumption. Although volatile compounds generally had only minor influences on consumption, alpha-pinene and camphor concentration were negatively related to pellet consumption, suggesting these monoterpenes may partially explain differential herbivory of individual tarbush plants by livestock.